Light refracting and magnifying envelop for incandescent lamps



(N M d l.)

o o e F. W. DUNLAP s; J. R. QUAIN. LIGHT REFRAGTING AND MAGNIFYNG BNVELP POR INCANDESCEN'I" LAMPS.

No. 597,964. Patented Jan. 25, 1898.

UNiTED STATES PATENT Erice.

i FOREST lVl'LLlAM DUNLAP AND OHN ROBERT QUAIN, OF LONDON, ENG- LAND, ASSIGNORS TO WILLIAM CASTNER CIIAPIN, OF SAN FRANCISCO,

OALIFOREIA. l

LFGHT REFRACTING AND MGNIFYING ENVLOP FOR INCANDESCENT LAMPS.

SPECIFICATION 4forming part of Letters Patent No. 597,964, dated January 25,v 1898.

I Application filed June 2, 1897. Serial No. 639.17% (No model.)

Our invention relatesto an improved light 1o refractingand magnifying envelop for incandescent lamps.' whereby the light-rays maryY be concentrated in the downward or any other Adirection in which increased illumination may` he required without thereby causing any i shadow to be projected in the opposite direction.

The invention is illustrated in the accompanying drawings and will be described with reference thereto; audit consists in envelop- 2o ing the bulb A of an ordinary'incandescent lamp or a Vpomitm-thereof in a light-refracting jacket B. B', constructed of one or more closely-wound spiral coils of glass rod of small circular or prismatic cross-section, so as to possess throughoutits length the property of a biconvex lens or of a prism, whereby the desired concentrating and magnifying effect is produced.

The glass rod is4 heated in the blowpipe- 3o flame and is closely wound upon a mandrel of corresponding shape to the lamp-bulb, the coils being in close juxtaposition, without, however, adhering to each other, so as toleave suiilcient `freedom to enable the coil to loef sprung over the bulb of the lamp in order that it shall retain itself thereon by the inherent elasticityV of the glass.V As, however,

y this elasticity is very limited it is necessary to make the complete envelop in two parts B 4c B', the one applied to the bulb from above and the other from below and meeting, prefy ter the light-'refracting envelop -has-been applied.

, In order to insure a permanent attachment of the spiral coil to the bulb and prevent displacement when the lamp is handled for thepurpose of being inserted in or removed from its holder or otherwise, the adjacent coils of the envelop B B are firmly united to each other (after the envelop has been applied upon the bulb) by transparent cement, such as ordinarily used for uniting broken glass or por-v celain; Similarly the upper convolution of the lower part B would be cemented to the lower convolution of the upper part B', and the convolutions of both parts may be cemented to the bulb A 'Where they touch it.

The glass rod 4'of which the al ove-described envelop is made may be of colorless or colored glass and may be clear or frosted, and the two parts of the envelop may be alike or 7o dierent in these respects, according to the requirements of the case.

W'here it is not required to apply the en- .velop to the .entire lamp,'the upper or the lower half may be employed, as may be required. Furthermore, when it is desired to project the light mainly in one particular direction, as in illuminating shop-fronts for the display of goods, the spirally-wound coil of glass may be applied to the side of the'lampbulb, as shown in Figure2, in which case the coils would lie in vertical instead of horizontal planes, the concave side of the spiral coil iitting closely to the bulb and being firmly attached thereto by transparent cement. f 8 5 Having now particularly described and ascertained the nature of the said invention and in what manner the same is to be performed, we declare that whatwe claim is l. The combination with an incandescent 9o electric-lamp bulb, of a light-.refracting envelop formed of a closely-wound spiral of glass rod of' circular or other section applied upon the bulb of the lamp substantially as specified.

2. As a new article of manufacture, alightrefractin g jacket forlamp-bulbs,comprising a rod of glass formed into coils and shaped to fit-upon the bulb, as set forth.

3. Alight-refracting jacket forlamp-bulbs, loo

comprising two Sections shaped to fit-upon tion being formed of a rod of glass coiled and envelop the bulb, each section being spirally, substantially as herein shown and 1o formed of e rod of glass coiled spirally, subdescribed.

. stantially as described.v FOREST WILLIAM DUNLAP.

4. Alight-reflectingjacketforlamp-bulbs, JOI-IN ROBERT QUAIN. consisting of an upper and lower seotion- YVitnesses: shaped to fit upon and envelop .the bulb, the T. W. KENNARD,

lowei` section being the larger and each sec- C. G. CLARK. 

